The invention relates to a construction equipment implement and method of operating a hydraulically activated implement component and more specifically a skid-steer implement having a hydraulically controlled grapple component.
Those familiar with the construction industry have long appreciated that construction equipment of the skid-steer front end loader type such as that shown in U.S. Pat. No. 3,231,114, when employed in a variety of different tasks are universally driven aggressively as they execute a multitude of construction chores. The aggressive manner in which skid-steer front end loader equipment is operated flows naturally from the very nature of the implements carried by the skid-steer loader arms. Typical implements include such apparatus as scarp buckets with grapple, single and double grapple buckets and manure forks with grapple to name a few. Each of these implements when secured to skid-steer front end loader arms on the front of the skid-steer loader engage either scrap, debris or other materials disposed or physically distributed along a surface upon which the skid-steer-loader is driven. The skid-steer loader with attached implement is normally driven in an aggressive fashion into materials sought to be moved. The momentum of the skid-steer loader and its attached implement coupled with the sudden reactive forces generated in the material to be moved by the impact of the implement and the material result in the implement being physically filled with the material. In order that the material that has been forced into the implement be held in place when the skid-steer loader moves to another location to deposit the material, the implement may include one or more hydraulically activated components that are pivotally mounted on the implement and move from an open unactuated position to a closed actuated position where the hydraulically actuated component forcefully grips the material between the component and implement to thereby secure the material in place during transit to a location where the material is to be deposited. When a skillful skid-steer loader operator is putting the skid-steer through its paces in the field, an observer of the skid-steer operator and his skid-steer loader will witness a symphony of coordinated activity of operator and skid-steer loader. As is well known, a skid-steer loader is a relatively small four wheel vehicle which is steered by braking or driving two wheels on one side of the vehicle while reversely driving the wheels on the other side of the vehicle. Two laterally spaced loader arms are mounted on the rear of the vehicle to swing upwardly and downwardly and, when the arms are swung downwardly their forward ends extend downwardly in front of the vehicle. A mounting plate is pivotally supported on the forward ends of the loader arms and normally support a construction implement such as a loader bucket. The very nature of the skid-steer loader as described above allows its operator to command the skid-steer loader to move forward and in reverse or to move in a tight circle about braked wheels of the loader while simultaneously opening or closing the hydraulically actuated component that cooperates with material forced into the implement. The most common manner in which the operator commands the hydraulically actuated component to open or close is to move a hydraulic control handle quickly from a fully open or unactuated position to a fully closed actuated position. The hydraulically activated component which is structurally heavy is therefore accelerated to significant velocities which induces momentum forces in the accelerated component. While the hydraulic actuation devices employed in moving the component are designed to move the component through a finite distance, the momentum, that is the mass and velocity of the component causes the component to continue its travel until it strikes a portion of the implement in what is called a hard stop. These hard stops cause the implement and the component to experience significantly high shock loading. The downside of this shock loading manifests itself in structural failures especially in bearings and bearing support structures of the implement and hydraulically actuated component.
To the question can an operator by careful attention to the movement of the hydraulic control lever avoid this shock loading, the answer is yes. In practice however a study of operator movement reveals that the operator may be simultaneously controlling a skid-steer loader movement and operation by the synchronized movement of both hands and feet at the same time. Accordingly normal skid-steer loader operation has the operator operating the loader at top speed to impact material to be carried by the implement and hydraulically actuated component that grips the material. It is not uncommon for the impact of the skid-steer implement with material to be moved to cause some of the material to pass physically through or by the component and implement resulting in damage to the hydraulic actuation apparatus or the skid-steer loader and/or its operator.
Typical of a work attachment or construction component of the type just described is shown in the F. P. Staken U.S. Pat. No. 5,565,885 (""885) issued Oct. 15, 1996. Of particular interest is a work attachment or component that includes a grapple hook mounted on the component by means of a set of two pairs of upstanding pivot brackets formed on the implement at opposite ends of the grapple hook. The grapple hook is caused to move from a fully open unactuated position to a fully closed actuated position by means of a pair of hydraulically actuated cylinders that are pivotally secured to each end of the implement and at the other end thereof to the grapple hook component.
When the grapple hook is moved quickly from an actuated position to an unactuated position severe shock loading is experienced in the pair of upstanding brackets and their respective pivot pins. It is this type of shock loading that eventually causes structural failure between the brackets and the implement of which they are a part. It is also to be noted that an open space between the pivot brackets at the opposite ends of the grapple hook allows ready passage of material being forced into the implement such that the material may pass through the implement and invade a front opening of the skid-steer cab and injure the skid-steer operator. The invention to be described hereinafter completely obviates shock loading problems of the nature experienced in the ""885 patent while simultaneously protecting the skid-steer loader operator and the hydraulic cylinder actuation component of the implement.
Simply stated the principal object of the invention is to provide a method and apparatus that prevents shock load damage to a construction implement when a hydraulically actuated component thereof is quickly driven from a fully actuated to an unactuated position or vice versa.
More specifically the invention is directed to a skid-steer loader implement having a hydraulically actuated grapple component that includes an implement having first and second spaced apart pivot support structures and a hydraulically actuated grapple component pivotally secured to the second pivot support structure. A hydraulically actuated cylinder has one end of the cylinder pivotally secured to the first pivot support structure of the implement and is provided with a moveable piston integrally coupled to an output actuation rod that is pivotally secured at an end remote from the piston to the grapple component. The hydraulically actuated cylinder has supply/return ports adjacent the ends of the cylinder adapted to be alternately coupled to a high pressure hydraulic fluid supply or low pressure hydraulic fluid return. The hydraulically actuated cylinder has valve structure to hydraulically cushion movement of the piston and associated actuation rod as the piston moves past a supply/return port prior to being physically stopped at the ends of the cylinder. The actuation rod is provided with a protective shield to protect the actuation rod surface from hostile environmental intrusions by objects in the vicinity of the actuation rod during actuation. The grapple component includes a pivot shaft portion that is at least as wide or substantially wider than a grapple tooth end of the grapple component. The second pivot support structure is comprised of a pair of bearing support elements spaced apart such that a grapple pivot shaft portion cooperates therewith to create a physical barrier to any material thing that may be gripped between the grapple component and implement.
Another object of the invention is to provide an apparatus that creates a cushioned stop for a hydraulically actuated grapple component of a skid-steer front end loader implement.
Yet another object of the invention is a method of operating a grapple component of an implement such that the speed of movement of the grapple component is slowed prior to reaching extremes of travel of the component established by the physical structure of the implement.
Still, yet another object of the invention is to provide a protective shield for an actuation rod of a hydraulically actuated cylinder in all stages of actuation.
A final object of the invention is to provide a bearing support structure for an implement such that a hydraulically actuated component that cooperates with the implement physically prevents any object handled by the implement and component to intrude past the implement and the component when the implement is in use.
In the attainment of the foregoing objects the invention contemplates as falling within the purview of the claims a skid-steer front end loader implement and a hydraulically actuated grapple component adapted for use with skid-steer loader arms, such that movement of the loader arms causes the implement and the grapple component to move therewith.
The implement when in use with the loader arms has a portion thereof located remote from the loader arms and another portion adjacent the loader arms. The implement portion adjacent the loader arms is provided with first and second spaced apart pivot support structures that have parallel pivot support axes. The hydraulically actuated grapple component is pivotally secured to the second pivot support structure.
At least one hydraulically actuated cylinder that has a tubular shaped barrel closed at one end thereof is pivotally connected at the closed end to a first pivot support structure. The barrel cooperates with a mating actuation piston mounted for reciprocation in the barrel. The actuation piston is integrally secured to one end of an actuation rod which slidably passes through a hermetically sealed opening in the other end of the barrel. The other end of actuation rod is pivotally connected to grapple component for movement therewith. The barrel is provided with a pair of spaced apart supply/return ports though a barrel wall. The supply/return ports are positioned adjacent the ends of the barrel. The closed end of the barrel and an end of the actuation piston cooperate to create a chamber therebetween. Whereas the other end of the actuation piston and the hermetically sealed opening in the other end of the barrel creates another chamber that includes therein the slidable actuation rod.
Alternatively hydraulically coupling one of the supply/return ports to a high pressure supply while simultaneously hydraulically coupling the other supply/return port to a hydraulic return results in a differential pressure existing across the actuation piston and causes the actuation piston and integral actuation rod to move and thereby cause the grapple component to pivotally move relative to the skid-steer implement.
In the most highly preferred embodiment of the invention the actuation piston is configured to cooperate with a supply/return port such that as an end of the actuation piston moves past either supply/return port, return flow of hydraulic fluid through the port is gradually diminished and movement of the actuation piston is cushioned near the end of the actuation piston travel which results in the grapple component experiencing a cushioned stop at both ends of its pivotal travel.
Another feature of the invention involves the actuation rod which has secured thereto at a point adjacent the actuation rod pivotal connection to the grapple component a protective shield member. The protective shield member extends toward the tubular shaped barrel and has an overall length greater than the actuation rod length when the actuation piston and rod are positioned at an end of the tubular barrel nearest the grapple component to be actuated. The protective shield is positioned such that relative movement of the actuation rod allows the protective shield member to continuously cover the actuation rod in all positions of the actuation rods sliding movement.
Another significant feature of the most highly preferred embodiment of the invention involves the structural nature of the grapple component which has a grapple tooth portion that includes a pivot shaft portion that may be wider than an end of the grapple tooth portion that may come in contact with the portions of implement remote from the loader arms when the hydraulically actuated grapple component is in a fully actuated position. The second pivot support structure is comprised of a pair of bearing support ears integrally secured to the implement and spaced apart such that the grapple tooth pivot shaft portion cooperates with the pair of bearing support ears such that the wider pivot shaft portion of the grapple tooth functions as a physical barrier to any material thing or object that may be gripped between the grapple tooth and implement that would damage the skid-steer loader if the grapple material should be forced toward the skid-steer loader absent the wider pivot shaft portion.
Other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.